This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A209031 #11 Mar 13 2017 05:19:34 %S A209031 1,4,12,88,625,5648,52208,505857,4992048,50169067,510807173, %T A209031 5260218485,54684221779,573168585795,6050541798221,64271927631233, %U A209031 686512535921878,7369066749454264,79449368494683376,859987831858141180,9342319735394175920,101820772577694786504 %N A209031 Number of n-bead necklaces labeled with numbers -7..7 allowing reversal, with sum zero and first differences in -7..7. %H A209031 Andrew Howroyd, <a href="/A209031/b209031.txt">Table of n, a(n) for n = 1..50</a> %e A209031 Some solutions for n=6: %e A209031 .-6...-3...-5...-3...-2...-5...-4...-4...-3...-5...-4...-4...-5...-3...-3...-5 %e A209031 .-4...-1...-4...-1...-2...-2....1...-3....0...-3...-1...-1...-5...-1...-2...-2 %e A209031 ..1...-2....2....5....0....2....0....1....1....4....2...-1....1...-1....4...-2 %e A209031 ..4...-1....1...-2....0...-1....2....4...-2...-1....0....4....5....6....4....5 %e A209031 ..6....5....6....0....2....4....0...-1....0....3....1....2....2...-1...-3....3 %e A209031 .-1....2....0....1....2....2....1....3....4....2....2....0....2....0....0....1 %Y A209031 Column 7 of A209032. %K A209031 nonn %O A209031 1,2 %A A209031 _R. H. Hardin_, Mar 04 2012 %E A209031 a(14)-a(22) from _Andrew Howroyd_, Mar 12 2017